Department of Engineering Mechanics, Tsinghua University, Beijing 100084, China.
Changqing Oilfield, PetroChina, Xi'an, Shaanxi 710018, China.
J Colloid Interface Sci. 2022 Dec;627:848-861. doi: 10.1016/j.jcis.2022.07.122. Epub 2022 Jul 21.
Preferential flow in porous media is commonly encountered and decreases the multiphase displacement efficiency. Here, we synthesized microgel-in-oil in suspension and demonstrated that microgel-in-oil as a novel additive could present self-adaptive transport behavior and introduce a novel multiphase displacement mode for improving displacement efficiency in heterogeneous porous media.
We investigated the microgel-in-oil formation process and characterized their morphology with fluorescence microscopy and Cryo-SEM. The suspension displacement performance in heterogeneous porous media was evaluated using a microfluidic chip containing a preferential flow pathway (PFP) and a parallel matrix region. The displacement results of microgel-in-oil were compared to plain microgel particles and analyzed from pore-scale particle transport behavior to macroscopic multiphase flow patterns.
The results show that suspension with moderate microgel-in-oil yields the optimal displacement efficiency. Fewer microgel-in-oil cannot alter the flow direction, while too many microgel-in-oil would block the PFP region. The topological analysis identified that suspensions with moderate microgel-in-oil content could achieve the strongest sweeping and carrying abilities that contribute to the highest displacement efficiency. The synergistic transport of microgel-in-oil and plain microgel particles would result in local pressure fluctuations to divert displacing fluid from PFP into the matrix region, which explains the above flow behavior.
多孔介质中的优先流普遍存在，并降低多相驱替效率。在这里，我们合成了悬浮态的油包微凝胶，并证明了油包微凝胶作为一种新型添加剂可以呈现自适应输运行为，并为改善非均质多孔介质中的驱替效率引入一种新型多相驱替模式。
我们研究了油包微凝胶的形成过程，并通过荧光显微镜和冷冻扫描电子显微镜对其形态进行了表征。使用包含优先流通道（PFP）和平行基质区域的微流控芯片评估了油包微凝胶在非均质多孔介质中的悬浮体驱替性能。将油包微凝胶的驱替结果与普通微凝胶颗粒进行了比较，并从孔隙尺度颗粒输运行为到宏观多相流动模式进行了分析。
结果表明，具有中等油包微凝胶含量的悬浮体可产生最佳的驱替效率。太少的油包微凝胶不能改变流动方向，而太多的油包微凝胶会堵塞 PFP 区域。拓扑分析表明，具有中等油包微凝胶含量的悬浮体可以实现最强的扫掠和携带能力，从而提高驱替效率。油包微凝胶和普通微凝胶颗粒的协同输运会导致局部压力波动，从而将驱替流体从 PFP 转移到基质区域，这解释了上述流动行为。
